=head1 SYNOPSIS
-For ease of access, the Perl manual has been split up into a number
-of sections:
-
- perl Perl overview (this section)
- perldata Perl data structures
- perlsyn Perl syntax
- perlop Perl operators and precedence
- perlre Perl regular expressions
- perlrun Perl execution and options
- perlfunc Perl builtin functions
- perlvar Perl predefined variables
- perlsub Perl subroutines
- perlmod Perl modules
- perlref Perl references and nested data structures
- perlobj Perl objects
- perlbot Perl OO tricks and examples
- perldebug Perl debugging
- perldiag Perl diagnostic messages
- perlform Perl formats
- perlipc Perl interprocess communication
- perlsec Perl security
- perltrap Perl traps for the unwary
- perlstyle Perl style guide
- perlapi Perl application programming interface
- perlguts Perl internal functions for those doing extensions
- perlcall Perl calling conventions from C
- perlovl Perl overloading semantics
- perlembed Perl how to embed perl in your C or C++ app
- perlpod Perl plain old documentation
- perlbook Perl book information
-
-(If you're intending to read these straight through for the first time,
-the suggested order will tend to reduce the number of forward references.)
-
-Additional documentation for perl modules is available in
-the F</usr/local/lib/perl5/man/man3> directory. You can view this
-with a man(1) program by including the following in the
-appropriate start-up files. (You may have to adjust the path to
-match $Config{'man3dir'}.)
-
- .profile (for sh, bash or ksh users):
- MANPATH=$MANPATH:/usr/local/lib/perl5/man
- export MANPATH
-
- .login (for csh or tcsh users):
- setenv MANPATH $MANPATH:/usr/local/lib/perl5/man
+B<perl> S<[ B<-sTuU> ]> S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]>
+ S<[ B<-cw> ] [ B<-d>[:I<debugger>] ] [ B<-D>[I<number/list>] ]>
+ S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal>] ]>
+ S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ]>
+ S<[ B<-P> ]> S<[ B<-S> ]> S<[ B<-x>[I<dir>] ]>
+ S<[ B<-i>[I<extension>] ]> S<[ B<-e> I<'command'> ]
+ [ B<--> ] [ I<programfile> ] [ I<argument> ]...>
+
+If you're new to Perl, you should start with L<perlintro>, which is a
+general intro for beginners and provides some background to help you
+navigate the rest of Perl's extensive documentation.
+
+For ease of access, the Perl manual has been split up into several sections.
+
+=head2 Overview
+
+ perl Perl overview (this section)
+ perlintro Perl introduction for beginners
+ perltoc Perl documentation table of contents
+
+=head2 Tutorials
+
+ perlreftut Perl references short introduction
+ perldsc Perl data structures intro
+ perllol Perl data structures: arrays of arrays
+
+ perlrequick Perl regular expressions quick start
+ perlretut Perl regular expressions tutorial
+
+ perlboot Perl OO tutorial for beginners
+ perltoot Perl OO tutorial, part 1
+ perltooc Perl OO tutorial, part 2
+ perlbot Perl OO tricks and examples
+
+ perlstyle Perl style guide
+
+ perltrap Perl traps for the unwary
+ perldebtut Perl debugging tutorial
+
+ perlfaq Perl frequently asked questions
+ perlfaq1 General Questions About Perl
+ perlfaq2 Obtaining and Learning about Perl
+ perlfaq3 Programming Tools
+ perlfaq4 Data Manipulation
+ perlfaq5 Files and Formats
+ perlfaq6 Regexes
+ perlfaq7 Perl Language Issues
+ perlfaq8 System Interaction
+ perlfaq9 Networking
+
+=head2 Reference Manual
+
+ perlsyn Perl syntax
+ perldata Perl data structures
+ perlop Perl operators and precedence
+ perlsub Perl subroutines
+ perlfunc Perl built-in functions
+ perlopentut Perl open() tutorial
+ perlpacktut Perl pack() and unpack() tutorial
+ perlpod Perl plain old documentation
+ perlpodspec Perl plain old documentation format specification
+ perlrun Perl execution and options
+ perldiag Perl diagnostic messages
+ perllexwarn Perl warnings and their control
+ perldebug Perl debugging
+ perlvar Perl predefined variables
+ perlre Perl regular expressions, the rest of the story
+ perlref Perl references, the rest of the story
+ perlform Perl formats
+ perlobj Perl objects
+ perltie Perl objects hidden behind simple variables
+ perldbmfilter Perl DBM filters
+
+ perlipc Perl interprocess communication
+ perlfork Perl fork() information
+ perlnumber Perl number semantics
+
+ perlthrtut Perl threads tutorial
+ perlothrtut Old Perl threads tutorial
+
+ perlport Perl portability guide
+ perllocale Perl locale support
+ perluniintro Perl Unicode introduction
+ perlunicode Perl Unicode support
+ perlebcdic Considerations for running Perl on EBCDIC platforms
+
+ perlsec Perl security
+
+ perlmod Perl modules: how they work
+ perlmodlib Perl modules: how to write and use
+ perlmodstyle Perl modules: how to write modules with style
+ perlmodinstall Perl modules: how to install from CPAN
+ perlnewmod Perl modules: preparing a new module for distribution
+
+ perlutil utilities packaged with the Perl distribution
+
+ perlcompile Perl compiler suite intro
+
+ perlfilter Perl source filters
+
+=head2 Internals and C Language Interface
+
+ perlembed Perl ways to embed perl in your C or C++ application
+ perldebguts Perl debugging guts and tips
+ perlxstut Perl XS tutorial
+ perlxs Perl XS application programming interface
+ perlclib Internal replacements for standard C library functions
+ perlguts Perl internal functions for those doing extensions
+ perlcall Perl calling conventions from C
+
+ perlapi Perl API listing (autogenerated)
+ perlintern Perl internal functions (autogenerated)
+ perliol C API for Perl's implementation of IO in Layers
+ perlapio Perl internal IO abstraction interface
+
+ perlhack Perl hackers guide
+
+=head2 Miscellaneous
+
+ perlbook Perl book information
+ perltodo Perl things to do
+
+ perldoc Look up Perl documentation in Pod format
+
+ perlhist Perl history records
+ perldelta Perl changes since previous version
+ perl58delta Perl changes in version 5.8.0
+ perl573delta Perl changes in version 5.7.3
+ perl572delta Perl changes in version 5.7.2
+ perl571delta Perl changes in version 5.7.1
+ perl570delta Perl changes in version 5.7.0
+ perl561delta Perl changes in version 5.6.1
+ perl56delta Perl changes in version 5.6
+ perl5005delta Perl changes in version 5.005
+ perl5004delta Perl changes in version 5.004
+
+ perlartistic Perl Artistic License
+ perlgpl GNU General Public License
+
+=head2 Language-Specific
+
+ perlcn Perl for Simplified Chinese (in EUC-CN)
+ perljp Perl for Japanese (in EUC-JP)
+ perlko Perl for Korean (in EUC-KR)
+ perltw Perl for Traditional Chinese (in Big5)
+
+=head2 Platform-Specific
+
+ perlaix Perl notes for AIX
+ perlamiga Perl notes for AmigaOS
+ perlapollo Perl notes for Apollo DomainOS
+ perlbeos Perl notes for BeOS
+ perlbs2000 Perl notes for POSIX-BC BS2000
+ perlce Perl notes for WinCE
+ perlcygwin Perl notes for Cygwin
+ perldgux Perl notes for DG/UX
+ perldos Perl notes for DOS
+ perlepoc Perl notes for EPOC
+ perlfreebsd Perl notes for FreeBSD
+ perlhpux Perl notes for HP-UX
+ perlhurd Perl notes for Hurd
+ perlirix Perl notes for Irix
+ perlmachten Perl notes for Power MachTen
+ perlmacos Perl notes for Mac OS (Classic)
+ perlmint Perl notes for MiNT
+ perlmpeix Perl notes for MPE/iX
+ perlnetware Perl notes for NetWare
+ perlos2 Perl notes for OS/2
+ perlos390 Perl notes for OS/390
+ perlos400 Perl notes for OS/400
+ perlplan9 Perl notes for Plan 9
+ perlqnx Perl notes for QNX
+ perlsolaris Perl notes for Solaris
+ perltru64 Perl notes for Tru64
+ perluts Perl notes for UTS
+ perlvmesa Perl notes for VM/ESA
+ perlvms Perl notes for VMS
+ perlvos Perl notes for Stratus VOS
+ perlwin32 Perl notes for Windows
+
+
+By default, the manpages listed above are installed in the
+F</usr/local/man/> directory.
+
+Extensive additional documentation for Perl modules is available. The
+default configuration for perl will place this additional documentation
+in the F</usr/local/lib/perl5/man> directory (or else in the F<man>
+subdirectory of the Perl library directory). Some of this additional
+documentation is distributed standard with Perl, but you'll also find
+documentation for third-party modules there.
+
+You should be able to view Perl's documentation with your man(1)
+program by including the proper directories in the appropriate start-up
+files, or in the MANPATH environment variable. To find out where the
+configuration has installed the manpages, type:
+
+ perl -V:man.dir
+
+If the directories have a common stem, such as F</usr/local/man/man1>
+and F</usr/local/man/man3>, you need only to add that stem
+(F</usr/local/man>) to your man(1) configuration files or your MANPATH
+environment variable. If they do not share a stem, you'll have to add
+both stems.
If that doesn't work for some reason, you can still use the
-supplied perldoc script to view module information.
+supplied F<perldoc> script to view module information. You might
+also look into getting a replacement man program.
If something strange has gone wrong with your program and you're not
sure where you should look for help, try the B<-w> switch first. It
=head1 DESCRIPTION
-Perl is an interpreted language optimized for scanning arbitrary
+Perl is a language optimized for scanning arbitrary
text files, extracting information from those text files, and printing
reports based on that information. It's also a good language for many
system management tasks. The language is intended to be practical
(easy to use, efficient, complete) rather than beautiful (tiny,
-elegant, minimal). It combines (in the author's opinion, anyway) some
-of the best features of C, B<sed>, B<awk>, and B<sh>, so people
-familiar with those languages should have little difficulty with it.
-(Language historians will also note some vestiges of B<csh>, Pascal,
-and even BASIC-PLUS.) Expression syntax corresponds quite closely to C
+elegant, minimal).
+
+Perl combines (in the author's opinion, anyway) some of the best
+features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
+those languages should have little difficulty with it. (Language
+historians will also note some vestiges of B<csh>, Pascal, and even
+BASIC-PLUS.) Expression syntax corresponds closely to C
expression syntax. Unlike most Unix utilities, Perl does not
arbitrarily limit the size of your data--if you've got the memory,
-Perl can slurp in your whole file as a single string. Recursion is
-of unlimited depth. And the hash tables used by associative arrays
-grow as necessary to prevent degraded performance. Perl uses
-sophisticated pattern matching techniques to scan large amounts of data
-very quickly. Although optimized for scanning text, Perl can also
-deal with binary data, and can make dbm files look like associative
-arrays (where dbm is available). Setuid Perl scripts are safer than
-C programs through a dataflow tracing mechanism which prevents many
-stupid security holes. If you have a problem that would ordinarily use
-B<sed> or B<awk> or B<sh>, but it exceeds their capabilities or must
-run a little faster, and you don't want to write the silly thing in C,
-then Perl may be for you. There are also translators to turn your
-B<sed> and B<awk> scripts into Perl scripts.
+Perl can slurp in your whole file as a single string. Recursion is of
+unlimited depth. And the tables used by hashes (sometimes called
+"associative arrays") grow as necessary to prevent degraded
+performance. Perl can use sophisticated pattern matching techniques to
+scan large amounts of data quickly. Although optimized for
+scanning text, Perl can also deal with binary data, and can make dbm
+files look like hashes. Setuid Perl scripts are safer than C programs
+through a dataflow tracing mechanism that prevents many stupid
+security holes.
+
+If you have a problem that would ordinarily use B<sed> or B<awk> or
+B<sh>, but it exceeds their capabilities or must run a little faster,
+and you don't want to write the silly thing in C, then Perl may be for
+you. There are also translators to turn your B<sed> and B<awk>
+scripts into Perl scripts.
But wait, there's more...
-Perl version 5 is nearly a complete rewrite, and provides
-the following additional benefits:
-
-=over 5
-
-=item * Many usability enhancements
+Begun in 1993 (see L<perlhist>), Perl version 5 is nearly a complete
+rewrite that provides the following additional benefits:
-It is now possible to write much more readable Perl code (even within
-regular expressions). Formerly cryptic variable names can be replaced
-by mnemonic identifiers. Error messages are more informative, and the
-optional warnings will catch many of the mistakes a novice might make.
-This cannot be stressed enough. Whenever you get mysterious behavior,
-try the B<-w> switch!!! Whenever you don't get mysterious behavior,
-try using B<-w> anyway.
+=over 4
-=item * Simplified grammar
+=item *
-The new yacc grammar is one half the size of the old one. Many of the
-arbitrary grammar rules have been regularized. The number of reserved
-words has been cut by 2/3. Despite this, nearly all old Perl scripts
-will continue to work unchanged.
+modularity and reusability using innumerable modules
-=item * Lexical scoping
+Described in L<perlmod>, L<perlmodlib>, and L<perlmodinstall>.
-Perl variables may now be declared within a lexical scope, like "auto"
-variables in C. Not only is this more efficient, but it contributes
-to better privacy for "programming in the large".
+=item *
-=item * Arbitrarily nested data structures
+embeddable and extensible
-Any scalar value, including any array element, may now contain a
-reference to any other variable or subroutine. You can easily create
-anonymous variables and subroutines. Perl manages your reference
-counts for you.
+Described in L<perlembed>, L<perlxstut>, L<perlxs>, L<perlcall>,
+L<perlguts>, and L<xsubpp>.
-=item * Modularity and reusability
+=item *
-The Perl library is now defined in terms of modules which can be easily
-shared among various packages. A package may choose to import all or a
-portion of a module's published interface. Pragmas (that is, compiler
-directives) are defined and used by the same mechanism.
+roll-your-own magic variables (including multiple simultaneous DBM
+implementations)
-=item * Object-oriented programming
+Described in L<perltie> and L<AnyDBM_File>.
-A package can function as a class. Dynamic multiple inheritance and
-virtual methods are supported in a straightforward manner and with very
-little new syntax. Filehandles may now be treated as objects.
+=item *
-=item * Embeddible and Extensible
+subroutines can now be overridden, autoloaded, and prototyped
-Perl may now be embedded easily in your C or C++ application, and can
-either call or be called by your routines through a documented
-interface. The XS preprocessor is provided to make it easy to glue
-your C or C++ routines into Perl. Dynamic loading of modules is
-supported.
+Described in L<perlsub>.
-=item * POSIX compliant
+=item *
-A major new module is the POSIX module, which provides access to all
-available POSIX routines and definitions, via object classes where
-appropriate.
+arbitrarily nested data structures and anonymous functions
-=item * Package constructors and destructors
+Described in L<perlreftut>, L<perlref>, L<perldsc>, and L<perllol>.
-The new BEGIN and END blocks provide means to capture control as
-a package is being compiled, and after the program exits. As a
-degenerate case they work just like awk's BEGIN and END when you
-use the B<-p> or B<-n> switches.
+=item *
-=item * Multiple simultaneous DBM implementations
+object-oriented programming
-A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB
-files from the same script simultaneously. In fact, the old dbmopen
-interface has been generalized to allow any variable to be tied
-to an object class which defines its access methods.
+Described in L<perlobj>, L<perlboot>, L<perltoot>, L<perltooc>,
+and L<perlbot>.
-=item * Subroutine definitions may now be autoloaded
+=item *
-In fact, the AUTOLOAD mechanism also allows you to define any arbitrary
-semantics for undefined subroutine calls. It's not just for autoloading.
+support for light-weight processes (threads)
-=item * Regular expression enhancements
+Described in L<perlthrtut> and L<threads>.
-You can now specify non-greedy quantifiers. You can now do grouping
-without creating a backreference. You can now write regular expressions
-with embedded whitespace and comments for readability. A consistent
-extensibility mechanism has been added that is upwardly compatible with
-all old regular expressions.
+=item *
-=back
-
-Ok, that's I<definitely> enough hype.
+support for Unicode, internationalization, and localization
-=head1 ENVIRONMENT
+Described in L<perluniintro>, L<perllocale> and L<Locale::Maketext>.
-=over 12
+=item *
-=item HOME
+lexical scoping
-Used if chdir has no argument.
+Described in L<perlsub>.
-=item LOGDIR
+=item *
-Used if chdir has no argument and HOME is not set.
+regular expression enhancements
-=item PATH
+Described in L<perlre>, with additional examples in L<perlop>.
-Used in executing subprocesses, and in finding the script if B<-S> is
-used.
+=item *
-=item PERL5LIB
+enhanced debugger and interactive Perl environment,
+with integrated editor support
-A colon-separated list of directories in which to look for Perl library
-files before looking in the standard library and the current
-directory. If PERL5LIB is not defined, PERLLIB is used.
+Described in L<perldebtut>, L<perldebug> and L<perldebguts>.
-=item PERL5DB
+=item *
-The command used to get the debugger code. If unset, uses
+POSIX 1003.1 compliant library
- BEGIN { require 'perl5db.pl' }
+Described in L<POSIX>.
-=item PERLLIB
+=back
-A colon-separated list of directories in which to look for Perl library
-files before looking in the standard library and the current
-directory. If PERL5LIB is defined, PERLLIB is not used.
+Okay, that's I<definitely> enough hype.
+=head1 AVAILABILITY
-=back
+Perl is available for most operating systems, including virtually
+all Unix-like platforms. See L<perlport/"Supported Platforms">
+for a listing.
-Apart from these, Perl uses no other environment variables, except
-to make them available to the script being executed, and to child
-processes. However, scripts running setuid would do well to execute
-the following lines before doing anything else, just to keep people
-honest:
+=head1 ENVIRONMENT
- $ENV{'PATH'} = '/bin:/usr/bin'; # or whatever you need
- $ENV{'SHELL'} = '/bin/sh' if defined $ENV{'SHELL'};
- $ENV{'IFS'} = '' if defined $ENV{'IFS'};
+See L<perlrun>.
=head1 AUTHOR
-Larry Wall <F<lwall@netlabs.com.>, with the help of oodles of other folks.
+Larry Wall <larry@wall.org>, with the help of oodles of other folks.
+
+If your Perl success stories and testimonials may be of help to others
+who wish to advocate the use of Perl in their applications,
+or if you wish to simply express your gratitude to Larry and the
+Perl developers, please write to perl-thanks@perl.org .
=head1 FILES
- "/tmp/perl-e$$" temporary file for -e commands
- "@INC" locations of perl 5 libraries
+ "@INC" locations of perl libraries
=head1 SEE ALSO
a2p awk to perl translator
s2p sed to perl translator
+ http://www.perl.com/ the Perl Home Page
+ http://www.cpan.org/ the Comprehensive Perl Archive
+ http://www.perl.org/ Perl Mongers (Perl user groups)
+
=head1 DIAGNOSTICS
-The B<-w> switch produces some lovely diagnostics.
+The C<use warnings> pragma (and the B<-w> switch) produces some
+lovely diagnostics.
-See L<perldiag> for explanations of all Perl's diagnostics.
+See L<perldiag> for explanations of all Perl's diagnostics. The C<use
+diagnostics> pragma automatically turns Perl's normally terse warnings
+and errors into these longer forms.
Compilation errors will tell you the line number of the error, with an
indication of the next token or token type that was to be examined.
-(In the case of a script passed to Perl via B<-e> switches, each
+(In a script passed to Perl via B<-e> switches, each
B<-e> is counted as one line.)
Setuid scripts have additional constraints that can produce error
The B<-w> switch is not mandatory.
Perl is at the mercy of your machine's definitions of various
-operations such as type casting, atof() and sprintf().
+operations such as type casting, atof(), and floating-point
+output with sprintf().
If your stdio requires a seek or eof between reads and writes on a
particular stream, so does Perl. (This doesn't apply to sysread()
While none of the built-in data types have any arbitrary size limits
(apart from memory size), there are still a few arbitrary limits: a
-given identifier may not be longer than 255 characters, and no
-component of your PATH may be longer than 255 if you use B<-S>. A regular
-expression may not compile to more than 32767 bytes internally.
+given variable name may not be longer than 251 characters. Line numbers
+displayed by diagnostics are internally stored as short integers,
+so they are limited to a maximum of 65535 (higher numbers usually being
+affected by wraparound).
+
+You may mail your bug reports (be sure to include full configuration
+information as output by the myconfig program in the perl source
+tree, or by C<perl -V>) to perlbug@perl.org . If you've succeeded
+in compiling perl, the B<perlbug> script in the F<utils/> subdirectory
+can be used to help mail in a bug report.
Perl actually stands for Pathologically Eclectic Rubbish Lister, but
don't tell anyone I said that.
The Perl motto is "There's more than one way to do it." Divining
how many more is left as an exercise to the reader.
-The three principle virtues of a programmer are Laziness,
+The three principal virtues of a programmer are Laziness,
Impatience, and Hubris. See the Camel Book for why.